Individual predictability of repeated spinal anaesthesia with isobaric bupivacaine.

To evaluate the individual predictability of the spread of spinal anaesthesia, an analysis of 38 patients who had had at least two spinal blocks within 4 years was performed. All spinal blocks were done with the patients in the lateral position at the midline in the interspace LIII-IV, injecting 3 ml of isobaric 0.5% bupivacaine. Regression analysis showed that the predictability of the maximal analgesic spread of the second anaesthesia from the first anaesthesia was highly significant (P less than 0.0001). Therefore, if a higher or lower level of the block is required, another method for the forthcoming anaesthesia may be needed. The reasons for this phenomenon could not be clarified in this retrospective study.